André Villas-Boas has made the acquisition of the Portugal midfielder João Moutinho a priority for Tottenham Hotspur as he plans an expensive overhaul of the squad at White Hart Lane.

Four months after losing his job at Chelsea, and three weeks after the dismissal of Harry Redknapp, the 34-year-old was confirmed as the head coach of Spurs on a three-year contract on Tuesday. The Portuguese has been joined by the first-team fitness coach, José Mário Rocha, and head of opposition scouting, Daniel Sousa – his staff during a triumphant season at Porto but also an ill-fated nine months at Stamford Bridge – and his arrival is likely to signal a hectic transfer period at the club.

The key issue facing Villas-Boas is the future of Luka Modric and a potential replacement for the influential Croatia international, who is wanted by Manchester United, Chelsea and Real Madrid. Despite having four years left on his contract, Modric is determined to leave after Spurs failed to qualify for the Champions League and having been denied the chance to join Villas-Boas at Chelsea last summer. Daniel Levy, the Tottenham chairman, is equally resolved to refuse the 26-year-old a move to a Premier League rival.

Villas-Boas is prepared for Modric's exit, however, and has identified Moutinho as his main transfer target. The pair enjoyed a glorious season together at Porto in 2010-11 – when Villas-Boas led the club to the league title with an unbeaten record, the Portuguese Cup and the Europa League – and the midfielder, who enhanced his reputation at Euro 2012, is keen on a reunion with his former coach. "AVB is one of the best coaches I've worked with," the 25-year-old said recently. "I'd work with him again tomorrow."

United have also been linked with Moutinho and Levy would have to sanction a club-record fee for Spurs to sign the Portugal international. Porto value him at €35m (£28m) and even a compromise fee would dwarf the £16.75m Tottenham paid Dinamo Zagreb for Modric in 2008.

Tottenham stand to make a lucrative profit on Modric and have moved for the Hoffenheim midfielder Gylfi Sigurdsson, who has rejected a £6.8m transfer to Swansea City and is stalling on a deal with Liverpool over personal terms. They also hope to complete the £9.5m signing of the Ajax defender Jan Vertonghen, despite problems over his release from the Amsterdam club, and the Internacional midfielder Oscar dos Santos Emboaba Júnior. They also need to improve a strikeforce that currently amounts to Jermain Defoe. Emanuel Adebayor remains a target after his successful loan last season but his £170,000-a-week wages at Manchester City are beyond Spurs.

Villas-Boas, who has been scouting in Brazil this summer, admires the Internacional striker Leandro Damião and Spurs have a sporting partnership with the Brazilian club. Gonzalo Higuaín and Ricardo Carvalho could also be used in a player-plus-cash deal with Real Madrid for Modric.

Levy, on welcoming the club's new head coach on Tuesday, said: "We are constantly looking to move the club forward. It is important that we now look to develop the potential within the squads at all levels, whilst strengthening the first team in the summer in key positions with players who will become part of the future success of the club."

Villas-Boas has been charged with the task of developing a younger team at Tottenham while qualifying for the Champions League, similar to the task he was given by Roman Abramovich at Chelsea only to alienate several senior and influential players before being sacked nine months into a three-year contract. His successor, Roberto Di Matteo, guided Chelsea to the FA Cup and Champions League double.

Levy considered several candidates to replace Redknapp, including the former France coach Laurent Blanc, the Everton manager, David Moyes, and Roberto Martínez of Wigan Athletic but quickly settled on Villas-Boas as his favoured choice and completed the appointment after further talks in London on Monday night. The Portuguese coach was unable to sign for another English club until after 1 July under the terms of his exit from Chelsea and is believed to have sought the European champions' permission to join Spurs before signing his contract.

Villas-Boas said: "Tottenham Hotspur is a great club with a strong tradition and fantastic support, both at home and throughout the world. I feel privileged to be its coach. For me this is one of the most exciting coaching positions in the Premier League. I have had several discussions with the chairman and the board and I share their vision for the future progress of the club. This is a squad any coach would love to work with and together I believe we can bring success in the seasons ahead."